This invention relates to an improved process for preparing methyl chlorosulfates by reacting methylene chloride with sulfur trioxide. This process is more efficient and cost effective as compared to those processes in current use.
Alkyl chlorosulfates, such as methyl chlorosulfates, have a variety of practical uses and are of current industrial interest and importance. These compounds are used extensively in organic synthesis where they are employed as intermediates in the synthesis of alkyl hydrogen sulfates, particularly long chain alcohols. Alkyl hydrogen sulfates are in turn useful as detergents builders. Alkyl chlorosulfates are also useful as alkylating agents and as chemical intermediates. See generally, E. Buncel, Chemical Reviews, Volume 70, page 323 (1970).
Recently, it has been discovered that certain alkyl chlorosulfates are useful reagents for the synthesis of chloromethyl esters of certain B-lactam antibiotics, such as penicillin acid sulfone. Chloromethyl chlorosulfate is particularly useful in such esterification reactions due to the mild reaction conditions, short reaction time and high yields which are achievable. In addition, bis(acyloxy) methanes are conveniently prepared using methylene bis(chlorosulfate). See E. Binderup and E. T. Hansen, Synthetic Communications, 14(9), pages 857 to 864 (1984).
Recently, it has been proposed to employ methylene bis(chlorosulfate) as an electrolyte in lithium batteries. Lithium batteries are of current interest for both military and commercial applications since they are capable of developing much higher voltages than other storage batteries of comparable size. Presently, thionyl chloride is used as the electrolyte of choice in lithium batteries. However, thionyl chloride has a relatively low vapor pressure which can cause the batteries to develop excessive pressure resulting in leakage of electrolyte from the battery container and failure of the battery. A non-volatile electrolyte having properties similar or superior to thionyl chloride would obviously represent an advance in this art.
Although the demand for methyl chlorosulfates has increased in recent years, the current technology for manufacturing such products is still relatively inefficient. Among the processes disclosed in the prior art are the reaction of alcohols with sulfuryl chloride, the reaction of alkyl sulfites with chlorine, and the alkylation of chlorosulfonic acid. These processes are summarized in E. Buncel, Chemical Reviews, supra. The reaction of chlorosulfonic acid with bromochloromethane to prepare chloromethyl chlorosulfate is also described in E. Binderup and E. T. Hansen, Synthetic Communications, supra.
The reaction of sulfur trioxide with either ethyl chloride or ethyl chloroformate to prepare ethyl chlorosulfate has also been reported. Similarly, sulfur trioxide can react with 1,2-dichloroethane to yield the chlorosulfate ClCH.sub.2 CH.sub.2 OSO.sub.2 Cl. However, the reported yields for these reactions are not high. See Chemical Reviews, supra.
It is therefore a principle object of the present invention to provide an improved process for preparing methyl chlorosulfates which is more efficient and cost effective than known processes.